The invention relates to a transparent substrate, in particular made of glass, provided with a thin-film stack including at least one metallic layer with infrared reflection properties, in particular a low-emissivity layer, arranged between two dielectric-based coatings.
The main application which the invention addresses is the use of such a substrate for the manufacture of thermal-insulation and/or solar-protection windows.
These are intended to be fitted both to buildings and to vehicles, in particular with a view to decreasing the air-conditioning workload and/or reducing excessive overheating entailed by the ever-increasing size of glazed areas in rooms and passenger compartments.
One type of thin-film stack well-known for giving a transparent substrate thermal properties, in particular low-emissivity properties, which is suited to the aforementioned required application consists of a metallic layer, in particular one made of silver, arranged between two dielectric-based coatings of the metal oxide type. This stack is, in the usual way, manufactured using a sequence of depositions carried out using a vacuum technique, for example sputtering, where appropriate assisted by a magnetic field.
A layer having a protective role for preventing degradation of the silver may also be provided in this stack.
In this type of stack, the silver layer essentially dictates the thermal, solar-protection and/or low-emissivity performance of the final window, whereas the dielectric layers primarily affect the optical appearance of the window obtained through interference. They furthermore have a function of protecting the silver layer against chemical and/or mechanical attack.
The improvements made to windows provided with stacks of the aforementioned type have so far allowed their field of application to be increased, while allowing them to keep a satisfactory level of thermal and optical performance.
Regarding the latter point, however, thermal performance is susceptible of yet further improvement, in particular with a lower insulation coefficient K being obtained.